1. Field of the Invention
The present invention(s) relate to at least one image forming apparatus that controls an interval between recording materials on which images are formed, and at least one feeding device related to, and for use with, same.
2. Description of the Related Art
Hitherto, in image forming apparatuses, such as copying machines and printers, productivity (that is, the number of sheets subjected to image formation per unit time) is increased by reducing an interval between recording materials when the recording materials are continuously conveyed. The phrase “interval between recording materials” refers to the distance between a trailing edge of a first recording material that is fed first, (that is, an end portion of the recording material at an upstream side in a conveying direction of recording materials) and a leading edge of a second recording material that is the next recording material fed after the first recording material (that is, an end portion of the recording material at a downstream side in the conveying direction of the recording materials). Here, when the interval between the recording materials is reduced, the first recording material and the second recording material may be conveyed while they are superposed upon each other when feeding or conveyance variations occur. Therefore, it is necessary to control the interval between the recording materials at a constant interval.
Japanese Patent Laid-Open No. 2000-335759 discusses an image forming apparatus including a sensor that detects a leading edge of a recording material fed from a cassette that accommodates recording materials. In the image forming apparatus, in accordance with a timing in which a leading edge of a first recording material that has been fed first is detected, a timing in which a second recording material is fed is determined. Therefore, for example, if a surface of a pickup roller that feeds the recording materials from the cassette is worn, and slippage occurs when the first recording material is being fed, the timing in which the leading edge of the first recording material is detected by the sensor is delayed. In this case, since the timing in which the second recording material is fed from the cassette is also delayed, it is possible to feed the first recording material and the second recording material with the interval between the recording materials being kept at a constant interval. That is, even if the timing in which the recording materials are fed is changed due to the influence of pickup roller slippage, the interval between the recording materials can be controlled at a constant interval.
However, in Japanese Patent Laid-Open No. 2000-335759, the timing in which the second recording material is fed is determined using the detection result provided by a particular sensor at all times. Therefore, when the length of the recording material in the conveying direction thereof is long, the time that is taken to feed the second recording material after the sensor has detected the leading edge of the first recording material is longer than that when the length of the recording material in the conveying direction thereof is short. As the time is increased, larger conveyance variations may occur.